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A procedure is described for the determination of nitrate in vegetable products, based on the quantitative reaction of nitrate and 2-sec-butylphenol in sulphuric acid (5 + 7), and the subsequent extraction and measurement of the yellow complex formed in alkaline medium. The colour reaction is sensitive and stable and absorbances measured a t 418 nm obey Beer's law for concentrations of nitrate-nitrogen between 0.13 and 2.50 p g ml-1. Various possible interferents in vegetable products do not interfere with the nitration of 2-secbutylphenol. Recoveries of nitrate from vegetable products were satisfactory and the standard deviation for the whole procedure was 1.41% for the 42 determinations; the detection limit of the method is 1.3 p.p.m. for nitratenitrogen.

An on-column fluorometric derivatization method has been developed for the determination of polyamines using highperformance liquid chromatography.The system for the derivatization consisted of a single-plunger pump and a reversed-phase C18 polymer column with a mobile phase of acetonitrile and alkaline borate buffer solution containing ophthalaldehyde and N-acetyl-L-cysteine as derivatizing reagents. The polyamines injected onto the liquid chromatograph are derivatized to fluorophores at the inlet of the column, followed by chromatography on the same column. Optimization of the liquid chromatography conditions led to a simple analytical method for the simultaneous determination of polyamines with high reproducibility and linearity. Application of this method to the determination of polyamines in food samples resulted in overall mean recoveries greater than 85% at fortification values of 20 -200 µg g-1 of each polyamine.high-performance liquid chromatographyPolyamines exist widely in biological materials and also in many food materials. In foods most of them are produced by enzymatic degradation associated with putrefaction or fermentation and show physiological activity in humans.1 Amine levels were shown to be a good index of food decomposition.2 The polyamines usually do not cause any hazards to individuals unless large amounts are ingested. However, some of the polyamines may be nitrosated in the presence of nitrite or act as precursors for other compounds capable of forming carcinogenic nitrosamines.3_s On the other hand, some of the polyamines are also known to potentiate histamine-toxicity6_S and to act synergistical1y9 in allergy-like food poisoning caused by the intake of histamine-contaminated food. Therefore, the determination of polyamines in foods is important. There has also been a need to develop a simple analysis method to determine polyamines in order to control the quality and evaluate the safety of various foods.A number of analytical methods, such as gas liquid chromatography (GC)10-12, enzymatic oxygen electrode method13 and high-performance liquid chromatography (HPLC)14-19 have been used so far for the determination of polyamines in foods as well as biological materials. However, the GC methods require a tedious derivatization procedure, while the enzymatic oxygen electrode method cannot distinguish one polyamine from another. Most reports on the HPLC method have employed the precolumn14-16 or postcolumn17-19 derivatization technique. However the precolumn methods suffer from some disadvantages16 such as requirements for carefully controlled reaction conditions and inferiority in reproducibility because of very limited stability. On the other hand, a postcolumn method is claimed to be less troublesome than a precolumn procedure and can eliminate its drawbacks. However, it requires expensive additional equipment for the chromatographic system, and the addition of a postcolumn reagent brings about peak broadening and dilution of samples. Furthermore, a gradient elution system has been requir...